In air conditioning installations for motor vehicles, it is known to provide an evaporator having an inlet branch and an outlet branch which are fastened to an expansion chamber and which, at least in the zone in which they meet the latter, are arranged substantially horizontally with one above the other (typically in a common vertical plane). In these known arrangements, the anchor plate bears on beads formed on the two branches, in order to compress sealing elements between the beads and suitable reception surfaces of the expansion chamber under the action of gripping or fastening means such as screws, which urge the anchor plate towards the expansion chamber. Such an anchor plate is in the form of an elongated plate having two slots formed through its thickness. These slots are open at the respective opposite ends of the plate. Each slot receives a respective one of the two branches, and each slot is in the form of an aperture having parallel edges, the width of which is slightly greater than the diameter of the corresponding branch of the evaporator, the slot being terminated in a semi-circular base portion the diameter of which corresponds to the width of the aperture. These slots are arranged back to back, with their median lines extending in the plane that contains the axes or geometrical centres of the semi-circular base portions.
In such installations, the expansion chamber is a relatively fragile component, which requires to be replaced quite often. When the anchor plate is disconnected from the expansion chamber and released, by unscrewing the screws, it tends to tilt on the lower branch in the plane which contains the axes of the two branches, so that it can then lie entirely within the space lying between the two branches, from which it can too easily slip sideways and fall out of reach. It is then hard to retrieve it from the bottom of the engine compartment of the vehicle. The danger of this happening is increased as the plane of the axes of the branches becomes more nearly vertical, since frictional effects between the branches and the edges of the slots become correspondingly reduced.